Rpm's @ highway speed

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tim johnson

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07 Ram 1500 5.7

Without knowing the rear end ratio I know this will be an open ended question but here goes...

At 70 mph how many rpm should I be turning? It stays around 2200. Just curious, on my 04 with the 4.7 at 70 mph it is lower. Just wondering if maybe the convertor is not going into lock up.

BTW, is there a tag or sticker somewhere that will tell me the gear ratio of the differential?


Thanks!
 
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Burntfire

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If MDS is engaged it will make the RPM's slightly higher.
 

glass3222

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you should have a tag in the glove box or on the rear axle that tells you the gear ratio.
 

truckin151

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With a 4.56 rear gear @70mph mine is turning right around 2300rpm

With the stock 3.92's @70mph it was right around 2100rpm
 

Graygoose

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3.92 with a 31" tall tire at 70mph is 2082. ( AOD calculated)
Yours have a 5 speed? If so, could be 3.55, with 5 speed 2155rpms. ( with 5 speed)
 
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truckin151

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3.92 with a 31" tall tire at 70mph is 2082.
Yours have a 5 speed? If so, could be 3.55, with 5 speed 2155rpms.

That's taking both OD gears into consideration right? 3.55s would give it a lower rpm than a 3.92 or 4.56. 2155 @ 70mph is about where mine is at with a 4.56 Rear gear.
 
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Graygoose

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sorry, corrected my post above
 
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truckin151

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Yes, with OD engaged on both.

99% positives that is incorrect then, a 3.55 rear gear will give you a lower rpm @70mph than a 3.92 and definitely lower than a 4.56 rear gear. Check your math again
 
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tim johnson

tim johnson

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Do you have Tow/Haul on when going 70mph?


Negative, Ghost Rider.

To me it feels like it is not going into the 2nd OD but I could be wrong. I have been driving an 04 with a 4.7 for the last 6 years.
 
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